Supervisor(s): The China Association for Science and Technology Sponsor(s): Chinese Optical Society；Shanghai Institute of Optics and Fine Mechanics，Chinese Academy of Sciences CN：31-1252/O4
Acta Optica Sinica(ISSN：0253-2239), founded in 1981, is the optical academic publication issued at home and abroad, which covers the latest research in optical science. The main scopes of this journal include atmospheric and ocean optics, detectors, fiber optics and optical communications, Fourier optics and optical signal processing, holography, imaging systems, measurement and metrology, lasers and laser optics, machine vision, materials, nonlinear optics, optical design and fabrication, optical devices, physical optics, quantum optics, remote sensing and sensors, spectroscopy, X-ray optics, etc. This journal offers service for optical science and technology researcher to carry out academic exchange and discussion. Acta Optica Sinica has been selected into Science Abstracts(SA), Chemical Abstract (CA), Abstract Journal(AJ), Information Service in Physics, Electro-Technology, Computer and Control (INSPEC), Engineering Index (EI), etc, which is one of 100 outstanding academic journals of China.
Advisory Editors Gan Fuxi Wang Zhijiang Xu Zhizhan Wang Runwen Editor-in-Chief Cao Jianlin Executive Editor-in-Chief Liu Liren Associate Editors-in-Chief Shao Jianda Xu Jinjun Hu Lili Han Shensheng Executive Editorial Board Wang Yongtian Liu Shu
Atom flux is one of the main factors influencing the quality of nano-gratings fabricated by atom lithography. Based on the theoretical model of eruption volume of atomic furnace tube, the atom flux levels for three typical kinds of furnace tubes are compared by the combination of theory and experiment. Moreover, with the best furnace tube configuration, the peak-to-valley height of the fabricated Cr nano-gratings increases up to 100 nm, which further optimizes the quality of nano-gratings.
A novel temperature and strain dual-parameter fiber sensor is proposed, which is constructed
via the cascading between a hollow core fiber and a fiber Bragg grating. The hollow core fiber confines the light to transmit inside the air core based on the anti-resonant mechanism and the light satisfying the resonance condition leaks out of the air core, which is indicated as a periodic loss peak in the transmission spectrum. Because the physical mechanisms for hollow core fiber and fiber Bragg grating as well as their spectral responses to external temperature and strain are different, the simultaneous measurement of temperature and strain can be realized based on the coupling matrix. The experimental results show that the temperature sensitivities of hollow core fiber and fiber Bragg grating are 24.55 pm/°C and 12.76 pm/°C near 1 550 nm wavelength, respectively. In contrast, the strain sensitivities are −0.70 pm/με and 1.02 pm/με, respectively. The proposed dual-parameter sensor is simple in fabrication and has high measurement accuracy.
Compared with the traditional laser altimetry technology, the photon-counting laser altimetry technology has the advantages of large data size, light weight, and high ranging precision, which is the development trend of laser altimetry technology. In this paper, we establish a mathematical model to study the characteristics of the photon-counting laser altimetry. The performance of the photon-counting laser altimeter is estimated by numerical calculation. The ground object model is established, and the simulation is carried out with Monte Carlo method. A filtering method for the altimetry data and an algorithm for optimizing the topography using the remote-sensing images are proposed. The results show that the root-mean-square error of the photon-counting laser altimeter is 6.1 cm under the condition of the noonday background with the most intense sun for the typical ground object model, and the error after optimization by the algorithm is 2.6 cm.
Calculation of nominal fixed grid, aimed to project a given area of the earth to the nominal image, is a key technique for navigation and registration of geostationary satellites. In view of the existing nominal fixed grid definitions from coordination group for meteorological satellites (CGMS) specification and geostationary operational environmental satellite-R series (GOES-R) user’s guide, whose representatives are FY-4A, Himawari-8, MTG, Electro-L satellites and GOES-R satellite, respectively, the formulas of CGMS and GOES-R nominal fixed grid calculation are deduced in detail, and the difference and relationship between CGMS and GOES-R nominal grids are summarized. Both nominal fixed grids are defined in satellite body Cartesian coordinate system. Furthermore, the detailed transforming process from nominal image of CGMS specification to the corresponding nominal image of GOES-R definition is presented using FY-4A observations. The results demonstrate that the nominal images defined by the two aforementioned methods can be converted to each other. Besides, by comparing the scanning and stepping angles of FY-4A advanced geosynchronous radiation imager to the responding angles of GOES-R fixed grid, the differences are 10
–16 μrad and 10
–17 μrad magnitude, respectively, which reveals that GOES-R fixed grid is defined from the point view of opto-mechanical design of advanced base imager. Considering that the foreign satellites, except GOES-R, all use CGMS fixed grid to calculate the nominal image. For end-user’s convenience, FY-4A nominal fixed grid will adopt the internationally accepted standard projection defined in CGMS LRIT/HRIT global specification.
A new method for the fabrication of a uniform side-glowing polymer optical fiber (POF) is investigated. The varied-line-space (VLS) grating scattering points are fabricated on the side of POF by laser-marking. The model of VLS grating scattering points by laser-marking is established, which is composed of shallow surface pits and scattering regions where scattering particles are distributed. The relative scattering power of scattering points and the calculating formula of VLS are derived theoretically. The change law of scattering light power of scattering points versus pit depth and particle density is analyzed. The distribution rule of VLS grating pitch versus pit depth and relative emissivity of side-glowing POF is also discussed. The results show that the tiny variation (μm level) of pit depth of scattering points has a great influence on scattering light power and VLS grating pitch. When scattering particle density is
N < 10
5 mm
−3, the variance of scattering light power with the scattering point density is small. In contrast, if the scattering particle density is
N > 10
5 mm
−3, the variance becomes obvious. The distribution curves of VLS grating pitch under different pit depths and relative emissivities are calculated theoretically, which are verified by experiments. In experiments, a side-glowing POF with a luminance uniformity of larger than 90% is obtained just by the adjustment of laser-marking power.
The computed laminography (CL) system has a unique advantage in aspects of large and plate-like objects imaging. We propose the parallel translation computed laminography (PTCL) system. Then, aiming at the image reconstruction of the system, the Feldkamp, Davis and Kress (FDK) algorithm is applied in the system. Due to the limited size of the detector, the system can only collect the projections of the region of interest of the object and the the total variation minimization based simultaneous algebraic reconstruction technique (SART + TV) algorithm is introduced into the object imaging. The simulation and experimental results demonstrate that both FDK and proposed method can achieve image reconstruction for PTCL. Compared with the FDK algorithm, the proposed method can reconstruct high-quality images from truncated and region of interest projections. Furtherly, it also demonstrates the feasibility of the system.
The concentration changes of exhaled carbon dioxide and water vapor are closely related to the physical condition. Therefore, it is of great significance to detect their concentrations. An exhaled gas detection device based on a 2.73 μm distributed feedback laser is proposed. Spectral lines at 3 659.402 cm
−1 and 3 659.934 cm
−1 are selected to measure carbon dioxide and water vapor respectively by using the wavelength modulation spectroscopy. The results show that using the second harmonic signal to calibrate the gas concentration, the linearity of 0.999 45 and 0.996 79 is obtained when the volume fractions of carbon dioxide and water vapor are less than 35% and 2.3%, respectively. The concentrations of carbon dioxide and water vapor during the respiratory cycle are measured in real time. With the measurement time of 0.92 s, the sensor achieves the detection sensitivity of 4.33 × 10
−3and 1.37 × 10
−4 for carbon dioxide and water vapor, respectively. At the acquisition time of 56.8 s, the detection accuracy with 0.12% of carbon dioxide is achieved, and a detection limit of 1.49 × 10
−4at the optimal integration time of 17 min is achieved for carbon dioxide measurement.
The existence of clouds in the atmosphere degrades the accuracy of aerosol retrieval. The empirical threshold method is popular in could detection. However, its strong subjectivity and difficulty in coping with the dynamic spatial-temporal changes of the environment or the difference among satellite-borne detectors result in a large classification error at the boundary of “cloud” and “clear”. In addition, its automatic detection is also poor. To achieve an effective detection of cloud over the land surface in the atmosphere, we propose a threshold optimized method which combines the statistical classification with data fusion of polarized multichannel remote sensing images. As for this method, a dual-brightness threshold to distinguish “cloud” from “clear” for most pixels is first derived based on the semi-supervised Kmeans clustering and its statistical features. Then, the joint confidence factor of multichannel data is calculated by the D-S evidence theory for each pixel in the fuzzy area of threshold neighborhood, and thus the fine threshold is acquired. The two objects of “cloud” and “clear” are finally and accurately classified in the sequential decision process. To validate the effectiveness of the proposed method, we perform a cloud detection experiment based on the remote sensing load data of POLRED3, and compare the measured results with the results of POLRED3. The results show that the classification by the proposed method is well consistent with that by the POLDER method with a high conformity of 95%. The error pixels are mostly located at the boundary between cloud and clear, indicating that the proposed method exhibits a favorable sensitivity to the classification at the cloud edge.
This study aims to propose a nanodisk structure embedding a rectangular metal block. The Fabry-Perot cavity formed by this structure is used to enhance the coupling effect of the surface plasmons. The structure has a narrow bandwidth, high quality factor, and high filtering performance. Herein, a multi-channel wavelength division multiplexer is constructed by multiple cavities coupling. The influence of the lateral and vertical widths of the rectangular metal block and the coupling distances between the embedded disk and rectangular metal block on the transmission characteristics of the device is described with the finite difference time domain method, for which a device without embedded rectangular metal block is used as the control group. A multi-channel wavelength division multiplexer is realized according to its transmission characteristics. The filter shows strong transmission characteristics when the disk resonance filter is embedded in the rectangular metal block; its full width at half maximum is significantly reduced and the quality factor is increased. By coupling a number of embedded rectangular metal block/disk resonators, we construct the filter. Such plasmon multi-channel wavelength division multiplexers can provide two- and three-channel demultiplexing functions. The resonant wavelength of each channel can be adjusted by selection of the parameters of the embedded metal block in the resonator. The transmission efficiency can reach up to 70%, and the minimum insertion loss is 1.549 dB. The average operating range is 189 nm, and there is no adjacent-channel crosstalk. We demonstrate that the proposed structure has good demultiplexing frequency characteristics.
In order to improve the detection accuracy of soil elements by laser-induced breakdown spectroscopy (LIBS), we establish a quantitative analysis model for soil elements of relevance vector machine (RVM), and it is compared with support vector machine (SVM) model and least squares support vector machine (LSSVM) model. The four characteristic lines of Ni element are taken as the analysis lines. After full spectral normalization, RVM, SVM and LSSVM models are established with the training sample set. According to the test results of testing sample sets, we can know that the SVM is inferior to the other models in terms of model prediction accuracy. However, in terms of model stability, LSSVM model is poorer than the other models. Therefore, in the practical applications, the advantages of RVM in model stability and prediction accuracy indicate that it is more suitable for quantitative analysis of LIBS.
